CONTRIBUTING EMPLOYEE OWNERSHIP PLAN (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Employer matching contributions to employee ownership plan	$ 6.9	$ 5.7	$ 5.2
Initial vesting period (in years)	2
Initial vesting period vested percentage	25.00%
Additional vesting percentage for each additional year of service	25.00%
Years of service for full vesting	5
Vesting percentage after five years	100.00%
Number of days an employee is prohibited from trading out of the fund to which the transfer was made	7

Additional vesting percentage for each year of service, after the initial two years of service.

No definition available.

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- Definition

Minimum term of service before an employee becomes vested in the plan.

+ References

No definition available.

+ Details

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- Definition

Initial vesting percentage after an employee completes two years of service.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Number of days employees are prohibited from trading out of the fund to which the transfer was made.

+ References

No definition available.

+ Details

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- Definition

Vesting percentage after an employee serves five years.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Number of years an employee serves before full vesting in the plan.

+ References

No definition available.

+ Details

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Data Type:	us-types:durationStringItemType
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- References

No definition available.

+ Details

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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